Effects Of Contusion Of Different Degrees On Repair Process Of Rat Skeletal Muscle And Its Application In Forensic Medicine

Objective:To study the morphological changes of acute inflammatory reaction,regeneration and repair of skeletal muscle in rats with different degrees of contusion,and to explore the assessment method of skeletal muscle injury degree,in order to establish the method of wound age estimation under the guidance of injury classification.Methods:To establish the rat right hindlimb skeletal muscle contusion model.The control group and the mild,moderate and severe contusion groups were set.Each contusion group included 1h,1.5h,2h,3h,4h,6h,1d,3d,5d,7d and 14d subgroup after injury.The regularity of injury,repair and regeneration of skeletal muscles at each time point were observed by HE staining.The changes of neutrophil numbers in skeletal muscles of rats in each group were detected by immunohistochemical staining.The TissueGnostics system was used to detect the number of effective nuclei,the number of neutrophils,and the mean migration distance of neutrophils in the injured area,and analyzes the relationship between these three parameters and the injury time under different degrees of contusion.Results:After contusion of skeletal muscles in rats,three parameters,namely the number of effective nuclei,the number of neutrophils,and the mean migration distance of neutrophils,can be used to infer the damage time for the corresponding degree of injury,and the combined use of the three parameters can further improve the accuracy of the wound age estimation under different degrees of contusion.When the number of neutrophils in the injured area is>600/mm~2 and the average migration distance of neutrophils is>250?m,the rats can be inferred to be 4h-6h after moderate contusion or 3h-6h after severe contusion of skeletal muscle.When the number of neutrophils is>1000/mm~2 and the average migration distance of neutrophils is>250?m,rats can be inferred to be 4h to 6h after severe contusion.When the number of effective nuclei is>3000/mm~2 in the injured area and the mean migration distance of neutrophils is>250?m,the rats can be inferred to be 3d after severe contusion.Conclusion:The injury and repair characteristics were different at the same time points after different degrees of skeletal muscle contusion in rats.The degree of injury will affect the wound age estimation.The number of effective nuclei,the number of neutrophils,and the mean migration distance of neutrophils all showed regular changes after skeletal muscle contusion,which can be used to distinguish the degree of injury and infer the injury time under the guidance of different degree of injury.Combined with three parameters which consist of the effective nuclei number,the neutrophil number,and mean migration distance of neutrophils,we can further determine the degree of damage,reduce the time window of wound age,and improve the accuracy of wound age estimation under the guidance of injury classification.